Large-scale synthesis of electrochemically active Titanium Diboride-based nanosheets by high-energy ball milling

Abstract

AlB2-type layered metal diborides have sought renewed research attention in recent years on account of their ability to yield XBenes?their quasi-two-dimensional (2D) counterparts. These quasi-2D nanostructures present exciting avenues to utilize the rich science offered by metal diborides. While a range of approaches have been developed to exfoliate layered metal diborides, the ability to obtain XBenes in a scalable manner is in its incipient stages?this is a critical bottleneck in translating their rich nanoscience into tangible technology. In this work, we present a scalable approach that employs high-energy ball milling to exfoliate titanium diboride (TiB2) into its quasi-2D counterparts at the gram scale. We first show that milling TiB2 crystals for an optimal duration (6 h) and at a specific balls-to-powder ratio (20:1) yields multi-layer-thick nanosheets (?5-10 nm thick). Second, by using Rietveld refinement and Raman spectroscopy, we show that the chemical integrity of TiB2 is retained to a large extent upon exfoliation?there is an associated formation of defects within the crystal structure of TiB2 that evolve with milling. Finally, we show that upon milling, the native electrochemical activity of TiB2 is enhanced by several folds. This ability to obtain nanosheets of TiB2 in a scalable manner using a high-energy ball mill bridges a critical missing link in the fast-growing science on nanoscaling AlB2-type metal borides.